Advanced, high-performance engines will require improved performance main shaft bearing compartment seals while also being required to meet more aggressive cost, weight, size, environmental and reliability metrics. Carbon seals may be manufactured to enable an engine and bearing compartment to function with minimal impact on Thrust Specific Fuel Consumption (TSFC), Thermal Management Systems (TMSs) and Lubrication Systems. Advanced engines require seals with improved wear resistance, improved performance, and improved reliability in order to meet customer, user, or program metrics.
Experience has demonstrated elevated seal wear and seal runner distress/deterioration, which results in increased air leakage characteristics and impacts the ability of a bearing compartment to contain oil. Future engines may experience elevated rubbing velocities relative to existing engine platforms, which could demand alternate solutions. A contacting, dry running seal can be limited by the capabilities of the materials selected. At elevated rubbing velocities, testing and experience have demonstrated that available materials are not able to withstand these conditions. Alternate solutions that have the high rubbing velocity capability, such as clearance seals (Knife Edge Lab, Controlled Gap, etc.) and Lift-Off Seals, present unique risks; system requirements may prevent their utilization.